The goals of this proposal are to gain further information on: (1) the biochemical changes in skeletal muscle of rats which cause atrophy during limb fixation with plaster casts; (2) the biochemical changes in skeletal muscle which permit (or do not permit) the rehabilitative growth of the atrophied muscle when the cast is removed; (3) methods which might prevent or slow atrophy of skeletal muscle in limbs fixed with plaster casts; and (4) methods which might speed the rehabilitative growth of atrophied skeletal muscle after casts have been removed from limbs.